Checking if login works after "Sorry, you are not allowed to edit this post."?

[velara3]

I'm getting an error message when I'm attempting to update a post.

How do I know if login is successful?

I'm able to get a list of posts so the endpoint works.

I'm using the following:

      var wp = new WPAPI({
            endpoint: apiRoot,
            username: username,
            password: credential,
            auth: true
      });

      var test = "posts";

      // get posts
      if (test=="posts") {
        log('verify endpoint')
          wp.posts().then(function( response ) {
                log("response", response)
            }).catch(function(error) {
                log("error", error)
            })
            return;
      }

    if (test=="update") {
        var postNumber = 28;

        var date = new Date()
        var time = date.getTime();
        var update = wp.posts().auth().id( postNumber ).update({
            title: "Time " + time
        })
        .then(function(response){
            console.log("complete");
            console.log(response);
        })
        .catch(function(err){
            log("error:", err);
        });
    }

I've installed and activated this plugin.

{ code: 'rest_cannot_edit',
  message: 'Sorry, you are not allowed to edit this post.',
  data: { status: 401 } 
}

Attempting to create a post returns this:

{ code: 'rest_cannot_create',
  message: 'Sorry, you are not allowed to create posts as this user.',
  data: { status: 401 } 
}

I'm using the download of wpapi.js (7/6/2017) here:

http://wp-api.org/node-wpapi/installation/

FYI I'm not on node. I'm in a client that runs ES6.